<p>
          Checks that each top-level class, interface or
          enum resides in a source file of its own.
          Official description of a 'top-level' term:<a class="externalLink" href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-7.html#jls-7.6">7.6. Top Level Type Declarations</a>.
          If file doesn't contains public class, enum or interface,
          top-level type is the first type in file.
        </p>